Propagator is responsible for injecting, not the RequestHandler (#108)

Author: chingor13

src/Trace/Propagator/HttpHeaderPropagator.php

@@ -76,8 +76,13 @@ public function extract($headers)
     public function inject(SpanContext $context, $container)
     {
         $header = str_replace('_', '-', preg_replace('/^HTTP_/', '', $this->header));
-        $container[$header] = $this->formatter->serialize($context);
-        return $container;
+        $value = $this->formatter->serialize($context);
+        if (!headers_sent()) {
+            header("$header: $value");
+        }
+        return [
+            $header => $value
+        ];
     }
 
     /**

src/Trace/RequestHandler.php

@@ -93,11 +93,7 @@ public function __construct(
         // If the request was provided with a trace context header, we need to send it back with the response
         // including whether the request was sampled or not.
         if ($spanContext->fromHeader()) {
-            if (!headers_sent()) {
-                foreach ($propagator->inject($spanContext, $headers) as $header => $value) {
-                    header("$header: $value");
-                }
-            }
+            $propagator->inject($spanContext, []);
         }
 
         $this->tracer = $spanContext->enabled()